104. Maximum Depth of Binary Tree.py

"""
https://leetcode.com/problems/maximum-depth-of-binary-tree/

Given the root of a binary tree, return its maximum depth.
A binary tree's maximum depth is the number of nodes along the longest path from the root node
down to the farthest leaf node.

Example 1:
    Input: root = [3,9,20,null,null,15,7]
    Output: 3

Example 2:
    Input: root = [1,null,2]
    Output: 2

"""


# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right


class Solution(object):
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if root is None:
            return 0

        return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1